视频:延迟是否仍在影响直播?

这段话摘自直播峰会的一个小组, Ooyala's Paula Minardi and Level 3's Jon Alexander discuss ongoing issues with 延迟 times and buffering and what viewers of live and VOD are inclined to tolerate as acceptable parts of the online video viewing experience.

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乔恩·亚历山大: We definitely see 延迟 as one of those kind of emotional subjects, 人们总是希望降低延迟. 为什么你要注册更高的延迟?

在广播方面, 这是一个有趣的轶事, 如果你谈论NFL, 视频的传播, 通过我们的网络进行广播, 大约10毫秒. If we do an encode on that, it adds about 100 milliseconds of 延迟. We've been seeing an increased number of broadcasters coming to us now asking for uncompressed feeds. 他们不希望我们做任何形式的压缩, 甚至是非常轻量级的无损压缩, 因为它增加了延迟. That is an additional 100 milliseconds of delay on the broadcast side that is something that they are trying to eliminate.

At the same time, they have to have a three-second delay imposed to avoid a Janet Jackson-type event. They are trying to trim off 100 milliseconds on one end, when they are imposing a three-second delay at another end. If you're doing satellite, your roundtrip time up and down is roughly a two-second delay. End-to-end delay, even in television best case, you're looking at 5-6 seconds. A lot less than the 30-40 seconds we typically see with HLS, but still non-zero.

对我来说, I think the biggest challenge with internet is it is non-deterministic and synchronization between devices isn't there. You could be watching on your phone, I could be watching on my phone and we're not synchronized. I think that's the experience which is more off-putting, rather than someone tweeting what's going to happen in five seconds time.

宝拉赛季: 我们和工作中的好人一起工作, 我们的一个合作伙伴, to look at buffering times and how that sort of impacts live and VOD content. 这很有趣. What we found is that the buffer ratio is that the buffer time over the session time. When we found that the buffer ratios were less than 0.2% that was kind of ideal for people to hang with the content. 如果你在视频点播流上看的话, 人们挂的时间大约是它的16倍, but they dropped off very quickly once that ratio started going up. On the live content, people hung on about 24 times as long.

What it sort of tells us is that maybe they are a little forgiving at this point around getting that experience, 因为他们重视这些内容. I think as time goes on they are going to be a little less forgiving, 尤其是年轻观众. 他们会开始提出要求.

乔恩·亚历山大: We definitely see 延迟 as one of those kind of emotional subjects, 人们总是希望降低延迟. 为什么你要注册更高的延迟?

宝拉赛季:我们与Nice People at Work合作, 我们的一个合作伙伴, to look at buffering times and how that sort of impacts live and VOD content. 这很有趣. What we found is that the buffer ratio is that the buffer time over the session time. When we found that the buffer ratios were less than 0.2% that was kind of ideal for people to hang with the content. 如果你在视频点播流上看的话, 人们挂的时间大约是它的16倍, but they dropped off very quickly once that ratio started going up. On the live content, people hung on about 24 times as long.